Pass the LPI LPIC Level 1 101-500 Questions and answers with CertsForce

One of the common reasons for the error message “device is busy” when trying to unmount a file system is that a user or a process has a file open in the mounted directory. This prevents the kernel from releasing the file system resources and detaching the device. To find out which user or process is holding the file system, one can use the lsof or fuser commands12. For example, lsof /mnt or fuser -m /mnt will list the processes that have open files in /mnt. To force the unmounting of a busy file system, one can use the -l option of the umount command, which will perform a lazy unmount. This means that the file system will be detached as soon as it is not busy anymore3. References: 1: How to solve “device is busy” problem in Linux 2: How to Find Out Which Process Is Using a File in Linux 3: umount(8) - Linux man page

The program that runs a command in specific intervals and refreshes the display of the program’s output is watch. This command is used to run any designated command at regular intervals and displays the output of the command on the terminal window. It is useful when you have to execute a command repeatedly and watch the command output change over time. The syntax of the watch command is:

watch [options] command

The options can modify the behavior of the watch command, such as how to format the output, how to handle signals, or how to enable color. The command is the command that you want to run and monitor. The default interval between each execution of the command is 2 seconds, but you can change it with the -n or --interval option. For more help using the watch command and its options, run man watch or visit this link.

The command that would disconnect the users and allow you to safely execute maintenance tasks on a disk partition is telinit 112. The telinit command is used to change the runlevel of the system, which is a mode of operation that defines what processes and services are running3. The runlevel 1, also known as single-user mode, is a mode that allows only the root user to log in, and disables all network services and graphical interfaces4. This mode is useful for performing system maintenance and recovery tasks, such as repairing a disk partition5.

The other options in the question are not correct because:

B. shutdown -r now: This command would reboot the system immediately, without disconnecting the users gracefully or allowing you to do any maintenance tasks.

C. killall -9 inetd: This command would kill the inetd process, which is a daemon that manages network services. This would not disconnect the users who are already logged in, and it would not stop other processes that might interfere with the maintenance tasks.

D. /bin/netstop --maint: There is no such command in Linux.

E. /etc/rc.d/init.d/network stop: This command would stop the network service, which would disconnect the users who are logged in remotely, but not the ones who are logged in locally. It would also not stop other processes that might interfere with the maintenance tasks.

 The function key that is used to start Safe Mode in Windows NT is none of the above, because Windows NT does not support Safe Mode. Safe Mode is a diagnostic mode of Windows that starts the system with minimal drivers and services, allowing the user to troubleshoot problems and restore the system to a normal state1. Safe Mode was introduced in Windows 95 and later versions, but not in Windows NT 4.0 and earlier2.

The other options are incorrect for the following reasons:

F10. This function key is used to access the Recovery Console in Windows XP, which is a command-line interface that allows the user to perform various administrative tasks, such as repairing the boot sector, restoring the registry, or copying files3. The Recovery Console is not the same as Safe Mode, and it is not available in Windows NT.

F8. This function key is used to access the Advanced Boot Options menu in Windows Vista and later versions, which allows the user to choose from various boot modes, including Safe Mode, Last Known Good Configuration, Debugging Mode, and others4. In Windows NT, pressing F8 during startup only displays a simple menu with three options: Normal, VGA mode, and Boot Logging5. None of these options are equivalent to Safe Mode.

F6. This function key is used to load additional drivers during the installation of Windows, such as SCSI or RAID drivers, from a floppy disk or a USB flash drive6. This function key has nothing to do with Safe Mode, and it is not relevant after the installation is completed.

 The environment variable LD_LIBRARY_PATH is used to tell the dynamic linker to look in a specific directory for some of a program’s shared libraries. It is a colon-separated list of directories that are searched by the dynamic linker when looking for a shared library to load1. The directories are searched in the order they are mentioned in. For example, if we have a program that depends on a shared library libfoo.so that is located in /home/user/build/lib, we can run the program with:

LD_LIBRARY_PATH=/home/user/build/lib ./program

This will instruct the dynamic linker to search for libfoo.so in /home/user/build/lib before the default directories. The environment variable LD_LIBRARY_PATH can also be appended to an existing value with the += operator, for example:

LD_LIBRARY_PATH+=:/home/user/build/lib

This will add /home/user/build/lib to the end of the LD_LIBRARY_PATH list. The other options are not valid environment variables for the dynamic linker. LD_LOAD_PATH, LD_LIB_PATH, and LD_SHARE_PATH are not recognized by the dynamic linker. LD_RUN_PATH is a linker option that can be used to embed a library search path in the executable at link time, but it is not an environment variable that can be set or modified at run time2. References:

LPI Exam 101 Detailed Objectives, section 1.101.3

ld-linux(8) — Linux manual page

Setting the dynamic linker with an environment variable - narkive

 The apt-get command upgrade will install the newest versions of all currently installed packages without removing any packages or installing new packages that are not already installed. It will only upgrade packages that can be upgraded without changing the dependencies1. The syntax is: apt-get upgrade. For example, apt-get upgrade nginx will update the nginx package to the latest version available in the repositories, if there is one2. The other options are not correct because:

auto-update is not a valid apt-get command.

dist-upgrade will also install new packages or remove existing packages if that is required to resolve a package conflict1. It is more aggressive than upgrade and may change the system in unexpected ways3.

install will install new packages or upgrade existing packages to the specified version1. It may also install or remove dependencies as needed4.

update will only resynchronize the package index files from the sources, but it will not install or upgrade any packages1. References:

apt-get(8) — apt — Debian buster — Debian Manpages

How to Update Nginx on Ubuntu 18.04 | Linuxize

What is “dist-upgrade” and why does it upgrade more than “upgrade”? - Ask Ubuntu

How to Install Specific Version of Package using apt-get - TecAdmin

 The dpkg command is a tool to install, build, remove and manage Debian packages. The option --remove is used to remove an installed package, but it does not remove the configuration files that may have been modified by the user. The option --purge is used to remove an installed package and also delete its configuration files. This can be useful if the user wants to completely uninstall a package and start from scratch if it is reinstalled later. The syntax is: dpkg --remove package or dpkg --purge package. For example, dpkg --remove nginx will remove the nginx web server package, but it will leave the configuration files in /etc/nginxdpkg --purge nginx will remove the nginx package and also delete the configuration files in /etc/nginx1. The other options are not correct because:

–remove only removes the program, --purge only removes the config files: This is false, because --purge also removes the program, not just the config files.

–remove removes a package, --purge also removes all packages dependent on it: This is false, because --purge does not remove any other packages, only the specified one. To remove a package and its dependencies, the apt-get command can be used with the option --auto-remove2.

–remove removes only the package file itself, --purge removes all files related to the package: This is false, because --remove also removes the files that are installed by the package, not just the package file itself. --purge only removes the configuration files that are not removed by --remove. References:

dpkg(1) — dpkg — Debian buster — Debian Manpages

How to remove a package and its dependencies with dpkg? - Ask Ubuntu

The command that can be used to download the RPM package kernel without installing it is yumdownloader kernel. This command is part of the yum-utils package, which contains a suite of helper tools for yum package manager. To use this command, you need to install the yum-utils package first1. The downloaded package will be saved in the current directory. You need to use root privilege because yumdownloader will update package index files during downloading. Unlike yum command, yumdownloader will not download any dependent packages1.

The other commands are either invalid or do not have the desired functionality. yum download --no-install kernel is not a valid yum command, as yum does not have a --no-install option2. rpm --download --package kernel is not a valid rpm command, as rpm does not have a --download or a --package option3. rpmdownload kernel is not a standard Linux command. rpm has a native support to download a package from a URL and install it, but not to download a package without installing it4.

The timeout option in a GRUB Legacy configuration file is used to define the amount of time (in seconds) that the GRUB menu will be shown to the user before booting the default entry. The timeout option is usually located in the /boot/grub/menu.lst file. For example, timeout 10 will display the GRUB menu for 10 seconds. To disable the timeout and wait for user input indefinitely, the value of timeout can be set to -1. To boot immediately without displaying the menu, the value of timeout can be set to 0. The other options are not valid for the GRUB Legacy configuration file. References:

GRUB Legacy - ArchWiki

How do I set the grub timeout and the grub default boot entry?

How to Remove the Timeout From GRUB Menu

The swapoff command is used to disable swapping on a device or a file. It takes the path of the device or file as an argument, or -a to disable all swaps. Disabling swap can improve the performance of the system if there is enough physical memory, or it can be necessary if the swap size needs to be changed. However, disabling swap can also cause problems if the system runs out of memory and has no swap space to use. References:

How to Disable Swap in Linux - Linux Handbook

How to Permanently Disable Swap in Linux? - GeeksforGeeks

LPI Linux Essentials - 1.1 Operating System Basics